St. Peter wrote this Epistle because he saw how the true, pure doctrine of faith had become falsified, darkened and suppressed. And he has wished to meet a two-fold error, springing from a wrong understanding of the doctrine of faith, and guard against it in both directions; namely, that we should not ascribe to works the power of making us righteous and acceptable before God, though these works belong to faith; and, on the other hand, that no one should think that there may be faith without good works. For if any one preaches concerning faith, that it justifies us without any addition of works, the people say, |One need do no works,| as we see it in our daily experience; and, on the other hand, when they fall on works and exalt them, faith must be prostrated, so that the middle way is one to be retained with difficulty, where there are not preachers of the right kind.
Now, we have ever taught this doctrine, that to faith we are to ascribe all things, one as well as another; that it alone makes us just and holy in the sight of God. Moreover, that if faith is present, out of it good works must and should proceed, since it is even impossible that we should pass this our life quite indolent, and do no works. Thus St. Peter in this Epistle would also teach us, and thus meet those who perhaps out of the former Epistle might have received the wrong apprehension that it sufficed for faith, though we should at the same time do no work. And against this the first chapter especially aims, wherein he teaches that believers should try themselves by good works, and become assured of their faith.
The second chapter is against those who exalt works merely, and depreciate faith. Therefore he admonishes them against the false teachers who should come, who, through the teachings of men, should destroy faith entirely. For he clearly saw what a cruel trial there would yet be in the world, as had even then already begun; as St. Paul says, II. Thes. ii., |The mystery of iniquity already works.|
Thus is this Epistle written as a warning for us, that we prove our faith by our good works, and yet that we trust not to our works.